Abstract
Abstract
In our paper, we study multiplicative properties of difference sets
$A-A$
for large sets
$A \subseteq {\mathbb {Z}}/q{\mathbb {Z}}$
in the case of composite q. We obtain a quantitative version of a result of A. Fish about the structure of the product sets
$(A-A)(A-A)$
. Also, we show that the multiplicative covering number of any difference set is always small.
Publisher
Canadian Mathematical Society